If the difference between your hands is not very marked, then this could be normal. A lot of what gives a part of the body its size is muscle mass, and if you exercise the muscles in one hand or arm more than the other, it may be slightly larger. For example, it is common for people to have slightly more strength (and size) in their dominant hand, especially if they work with their hands a lot.
Hormonal problems are unlikely. These tend to cause over all problems with the size of the body and they wouldn't typically affect just one part of the your body, such as your hand.
If you take a close look at your entire body and notice that the asymmetry is not limited just to your hand but also extends to the rest of that side of your body, this could be a condition that is known as hemihypertrophy. You should see your doctor
for an evaluation to be on the safe side. In adulthood, hemihypertrophy is a fairly benign condition. However, as there is a higher risk of certain types of cancers, it should be evaluated. You do not have hemihypertrophy, however, if the size discrepancy is just your hand.